Neuromodulatory regulation of synaptic plasticity in spinal nociceptive circuits

项目摘要/摘要 初级传入突触对脊髓投射神经元的长时程增强作用 与疼痛敏感度增加有关。控制成人PNS中LTP的产生的定时规则可以 因新生儿组织损伤而持续放松，这可能有助于早期生命损伤的能力 “启动”伤害性回路，从而在随后的侮辱后加剧疼痛。在大脑中，临时的 G蛋白偶联强烈调控这种峰时依赖性可塑性(STDP)的窗口 多巴胺(DA)等神经调节剂引起的受体(GPCR)信号转导。这增加了一种可能性，即 新生儿损伤促进初级传入突触向成年三叉神经节的LTP，从而促进持续性 疼痛，通过脊髓神经调节信号的长期变化。不幸的是，目前还不清楚是如何 GPCRs影响感觉突触至三叉神经节的STDP。因此，细胞和分子机制 成体背角上行伤害性信息传递增强的基础 人们对启动状态知之甚少。此应用程序的目的是识别神经调节 促进感觉突触活动依赖性加强的信号传递到关键的输出神经元。 脊髓伤害性环路参与了早期生命损伤后疼痛通路的启动。 中心假说是，脊髓三叉神经节感觉突触上的非Hebbian长时程增强是由D1样分子启动的 (即d1/d5)多巴胺受体激活，与依赖mGluR5的细胞内钙离子同时发生 释放和细胞外信号调节激酶(ERK)信号，这是新生儿启动所必需的。这个 这项拟议研究的基本原理是，这些研究将确定新的分子策略来减少 脊髓伤害性神经网络的信号增益。在强劲的初步数据的指导下，中心假说将 通过追求以下特定目标进行测试：(1)阐明DA受体激活如何塑造STDP PNS；(2)确定与DA受体协同促进PNS LTP的信号通路；以及(3) 确定介导新生儿组织脊髓伤害性环路启动的神经调节剂 损坏。这些目标将通过使用多学科实验方法来实现，其中包括 PNS中STDP结合反射和非反射行为的电生理特征 疼痛的程度。这项拟议的工作具有创新性，因为它将第一次证明DA信令 规定了支配感觉突触对脊髓三叉神经节可塑性的时间规则。这些措施的结果 研究将确定新的脊椎机制，以增强伤害性传递到 大脑，以及异常的神经调节有助于脊髓的持续性敏化 早期组织损伤后的伤害性回路。因此，拟议的研究具有重要意义，因为它将提供 设计新的干预策略以扰乱脊髓LTP作为缓解 减少慢性疼痛，最大限度地减少新生儿组织损伤对发育中的中枢神经系统的长期影响。

Project Summary/Abstract Long-term potentiation (LTP) of primary afferent synapses onto spinal projection neurons (PNs) has been linked to increased pain sensitivity. The timing rules controlling the generation of LTP in adult PNs can be persistently relaxed by neonatal tissue damage, which likely contributes to the ability of early life injury to ‘prime’ nociceptive circuits and thereby exacerbate pain after subsequent insult. In the brain, the temporal window governing this spike timing-dependent plasticity (STDP) is strongly regulated by G protein-coupled receptor (GPCR) signaling evoked by neuromodulators such as dopamine (DA). This raises the possibility that neonatal injury facilitates LTP at primary afferent synapses onto adult PNs, and thereby promotes persistent pain, via long-term changes in spinal neuromodulatory signaling. Unfortunately, it remains unknown how GPCRs influence STDP at sensory synapses onto PNs. As a result, the cellular and molecular mechanisms underlying the increased amplification of ascending nociceptive transmission by the adult dorsal horn during the primed state are poorly understood. The objective of this application is to identify the neuromodulatory signals that promote the activity-dependent strengthening of sensory synapses onto the key output neurons of the spinal nociceptive circuit and contribute to the priming of developing pain pathways after early life injury. The central hypothesis is that ‘non-Hebbian’ LTP at sensory synapses onto spinal PNs is enabled by D1-like (i.e. D1/D5) dopamine receptor activation, occurring in concert with mGluR5-dependent intracellular Ca2+ release and extracellular signal-regulated kinase (ERK) signaling, which is essential for neonatal priming. The rationale of the proposed research is that these studies will identify novel molecular strategies to reduce the signaling gain of the spinal nociceptive network. Guided by strong preliminary data, the central hypothesis will be tested by pursuing the following specific aims: (1) Elucidate how DA receptor activation shapes STDP in PNs; (2) Identify the signaling pathways which cooperate with DA receptors to facilitate LTP in PNs; and (3) Identify the neuromodulators which mediate the priming of spinal nociceptive circuits following neonatal tissue damage. These aims will be accomplished by using a multidisciplinary experimental approach that includes electrophysiological characterization of STDP in PNs combined with both reflexive and non-reflexive behavioral measures of pain. The proposed work is innovative because it will be the first to demonstrate that DA signaling dictates the timing rules governing the plasticity of sensory synapses onto spinal PNs. The outcome of these investigations will be the identification of new spinal mechanisms that augment nociceptive transmission to the brain, and the demonstration that aberrant neuromodulation contributes to the persistent sensitization of spinal nociceptive circuits after early tissue damage. Thus the proposed research is significant because it will provide knowledge needed to design novel interventional strategies to disrupt spinal LTP as a means to alleviate chronic pain and to minimize the long-term consequences of neonatal tissue injury for the developing CNS.